This invention relates to an improved apparatus for producing spirally formed pipe. More particularly this invention relates to a pipe cutting apparatus having dual external cutting knives for cutting spirally formed pipe rapidly and efficiently.
A large potential for small diameter spiral pipes exists in the filter market, such as for use in automobile oil filters. These filters typically have a perforated inner metal cylinder that is approximately one inch in diameter. Because spiral pipes such as those used in oil filters need to be accurately and cleanly cut in large quantities, a pipe forming and cutting apparatus capable of fast and accurate cuts is necessary.
There are several known ways to form and cut a pipe. A pipe may be formed by spirally or helically winding a continuous strip of metal and joining adjacent edges of the wound strip to form a spiral lockseam in the pipe. In some pipe forming and cutting machines, the spirally formed pipe is cut by moving a knife outside the pipe into an overlapping position with a knife inside the pipe. Other types of spiral pipe forming and cutting machines use multiple knives or rotate the knives around the pipe to cut the pipe into sections.
Increased cutting speed in a spiral pipe forming and cutting apparatus is desirable in order to increase pipe production capabilities. One type of pipe cutting machine uses a single rotatable knife in a fixed position with respect to the pipe. The spiral pipe makes a full rotation before a cut is complete using this type of pipe cutting machine. Pipe cutting machines using a knife or knives that rotate around the pipe while cutting are generally more complicated and expensive than pipe cutting machines using fixed knives.
Accordingly, a spiral pipe forming and cutting apparatus is necessary that can improve productivity and sever a continuously formed spiral pipe rapidly and efficiently. Furthermore, a pipe cutting apparatus capable of cutting pipe lengths shorter than the width of the metal strip used to form the spiral is desirable.